I. FIELD OF THE INVENTION
This invention relates to wet/dry explosive packages and methods for use of same and more particularly to pre-weighed, pre-sized, explosive containment packages suitable for use with a variety of blasting agents and suitable for use in small bore holes with diameters of three and one half inches (3.5") or less.
II. PRIOR ART AND OTHER CONSIDERATIONS
The drilling of bore holes in typical blasting operations, such as road construction or strip mining, represents a substantial percentage of the total cost of such operations. Present methods and devices for these blasting operations require bore holes of at least four inches (4") in diameter and sometimes as large as six inches (6") in diameter for proper detonation and propagation of the blasting agent. One typical blasting agent in wide commercial use today is a dry blasting agent commonly known within the industry as AN/FO. AN/FO is a mixture of ammonium nitrate and fuel oil. AN/FO provides excellent performance as an explosive at a reasonable cost and excels in gas production during detonation while providing a moderately high detonation velocity. A major disadvantage of AN/FO is that it is water soluble and cannot be used unprotected in wet holes due to obvious desensitization problems. Various containment devices have been proposed for utilizing AN/FO or similar blasting agents in wet bore hole situations, however, these devices and methods have produced only marginal success and require bore hole diameters of at least four inches (4") for proper loading, detonation, firing consistency and propagation.
Blasting operations of the type described herein typically require that a number of bore holes be drilled within a calculated distance of each other with the holes being detonated or "fired" in a sequential and timed order. Water-bearing blasting agents, such as explosive emulsions, slurries or gels, have been successfully used in wet hole situations, however, these agents, used alone, have a tendency to "dead press" in small diameter, close pattern bore hole operations and have, therefore, been generally unsuitable for such operations. "Dead pressing" occurs when the oxygen-carrying glass beads contained within the water-bearing blasting agent are shattered by the shock waves from the blast of the previous sequential blast hole thereby prematurely releasing and dissipating the oxygen within the beads which tends to neutralize the explosive force within the "dead pressed" hole. Prior art explosive containment devices have been unable to eliminate or prevent the problem of dead pressing.
Additional problems with the prior art containment devices include poor cartridge-to-cartridge propagation, poor detonation, tedious loading requirements, inconsistent firing and high overall cost.
It would be expedient, therefore, for the provision of method and apparatus for the containment of water sensitive and/or water-bearing blasting agents and related components which can be effectively and efficiently used in wet or dry bore hole applications wherein the bore hole diameter is required to be no larger than three and one half inches (3.5").
In view of the foregoing, it is an object of this invention to provide method and apparatus for a wet/dry, small bore hole, explosive device which can be used effectively and efficiently in wet or dry bore holes of three and one half inches (3.5") or less diameter.
An advantage of the present invention is the provision of method and apparatus for a wet/dry, small bore hole, explosive device which assures propagation along a continuous column of explosives.
An advantage of the present invention is the provision of method and apparatus for a wet/dry, small bore hole, explosive device which will consistently fire in wet hole conditions.
Another advantage of the present invention is the provision of method and apparatus for a wet/dry, small bore hole, explosive device which has excellent detonation characteristics and efficiencies.
Another advantage of the present invention is the provision of method and apparatus for a wet/dry, small bore hole, explosive device which contains pre-weighed, pre-packaged, blasting agents for improved blast control and safety.
Yet another advantage of the present invention is the provision of method and apparatus for a wet/dry, small bore hole, explosive device which produces less fly rock, less noise and vibration and less chance for bore hole overloading.
A further advantage of the present invention is the provision of method and apparatus for a wet/dry, small bore hole, explosive device which effectively assembles one or more blasting agent(s) and blast detonation components within a single protective containment vessel.
A further advantage of the present invention is the provision of method and apparatus for a wet/dry, small bore hole, explosive device which eliminates the problem of "dead pressing" when using a water-bearing blasting agent.
A further advantage of the present invention is the provision of method and apparatus for a wet/dry, small bore hole, explosive device which substantially reduces the cost of the overall blasting operation.